Electronic properties of the Kondo lattice U2Pt2Sn

Abstract

The magnetization $M(T,H)$, specific heat ${C}_{p}(T,H)$, ${}^{195}$Pt and ${}^{119}$Sn NMR Knight shifts $K(T)$, electrical resistivity $\ensuremath{\rho}(T)$, and magnetoresistance $\text{MR}(T,H)$ measurements were performed on a polycrystalline sample of antiferromagnetic compound U${}_{2}$Pt${}_{2}$Sn with the N\'eel temperature ${T}_{N}$ $=$ 15.7 K. It is found that the ${C}_{p}(T)$ and $\ensuremath{\rho}(T)$ data in the antiferromagnetic state may be interpreted with help of the spin-wave theory with a magnon gap $\ensuremath{\Delta}/{k}_{B}\ensuremath{\sim}6$--10 K. Furthermore, analysis of the experimental data allows us to conclude that U${}_{2}$Pt${}_{2}$Sn is a dense Kondo system, in which the exchange interaction, Kondo effect, and crystalline electric field compete with each other on the energy scale ${T}_{N}<{T}_{K}<{\ensuremath{\Delta}}_{\text{CEF}}$. The Kondo-lattice component of the ${}^{195}$Pt and ${}^{119}$Sn NMR Knight shift has been fitted to the two-fluid model for heavy fermions ${K}_{\text{KL}}\ensuremath{\propto}(1\ensuremath{-}T/{T}^{*})\mathrm{ln}({T}^{*}/T)$ with a characteristic temperature ${T}^{*}\ensuremath{\sim}$ 80 K. Electronic properties of heavy-fermion state in U${}_{2}$Pt${}_{2}$Sn are discussed in the context of the Wilson ratio (${R}_{W}$ $=$ 2.8), Kadowaki-Woods-Tsujii ratio [$A/{\ensuremath{\gamma}}^{2}\ensuremath{\sim}$ 2.15 $\ifmmode\times\else\texttimes\fi{}$ 10${}^{\ensuremath{-}5}\phantom{\rule{0.28em}{0ex}}\ensuremath{\mu}\ensuremath{\Omega}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}/(\mathrm{mJ}/{\mathrm{mol}}_{\mathrm{U}}\phantom{\rule{0.16em}{0ex}}\mathrm{K})}^{2}$ with $N$ $=$ 2], and an empirical ratio $R={T}^{*}/{T}_{K}\ensuremath{\sim}2$.